code: def sigmoid(expr, to_reuse=False):
      neg_expr = ast.BinNumExpr(
          ast.NumVal(0.0), expr, ast.BinNumOpType.SUB
      )
      exp_expr = ast.ExpExpr(neg_expr)
      return ast.BinNumExpr(
          ast.NumVal(1.0),
          ast.BinNumExpr(
              ast.NumVal(1.0), exp_expr, ast.BinNumOpType.ADD
          ),
          ast.BinNumOpType.DIV,
          to_reuse=to_reuse,
      )
  
file_path: m2cgen/m2cgen/assemblers/fallback_expressions.py
imports: import math
  from m2cgen import ast
  from m2cgen.assemblers import utils
label_desc: Use image node_id 7 for calling a global function with example usage: sigmoid(expr, to_reuse) and returns: ast